There have been many devices for analyzing assay substances in the market, and particularly, there are also some related invention patents. For example, EP291194 discloses a cross-flow immunoassay device for testing HCG, which is a single-use test strip that requires a user to interpret the results. However, the interpretation of results has a degree of subjectivity, and a timer should also be provided. On the other hand, the result is displayed by color which will deepen with time and then affect the interpretation of the result. EP653625 discloses a device which gets results by using an optical method; in that device, the test strip disclosed by EP291194 is inserted into a reader, with positioning the strip on an optical element of the reader. The strip is lighted by the light emitted from a light source, and then the reflected or transmitted light will be detected by an optical detector. Typically, the reader includes at least one light-emitting diode (LED), and for each LED, a corresponding optical detector is provided, which belongs to a reusable electronic pen. In a similar analytical device like the above, it is needed to carefully position the analytical reader and the test strip, since a small displacement of a detection or control zone in relation to a corresponding optical detection zone will significantly affect the detector readings due to the quite weak visible signals formed in the detection zone and the control zone. In addition, it is very important that the optical detector must be close to the test strip, because the amount of light captured by a light sensitive diode is very small, and the strength of signal decreases rapidly with the increasing distance from the strip to the detector, for the signal strength usually complies with inverse square law. Thus, the user should carefully position the test stick and the readout of analytical results, particular for a household device. However, for a reusable analytical device, especially for such small-type device, it is easily to cause dislocation by repeated insertions of the strip, while a tiny dislocation will in turn cause an inaccuracy. The replacement of a strip may be result in an improper installation, and then lead to a misjudgment caused by a tiny inaccuracy of the reader which is inherently sensitive to the optical path length.
U.S. Pat. No. 5,837,546 discloses an automatic assay device and method. The device provides an additional electrode by a cross-flow carrier, detects if there is fluid on the carrier, generates a signal to turn on the electronic assay device, and displays the testing result. However, in different tests, the liquid flows along the carrier at different speeds, and different types of flow rate characteristics of liquids will result in inaccuracy readings. Due to the inconsistent characteristics of the materials of the wick and the porous, water-permeable film, the best time for reading will be different.
CN 1573315B discloses a device for reading the analytical results performed by a liquid transporting carrier. This device is directed to solve the problem of how to determine the best reading time, but it cannot solve the problem of different fluids having different flow-rate standards. Meanwhile, for some assay devices, their required detection times are too long, for example, an assay-based, commercial cross-flow detection tool for detecting heart injury takes up to 15 minutes to finish the assay.
CN 1573316B discloses an optical device for assay reading, which also includes a light source and an optical detector, but the device is somewhat complicated and has many more optical paths, thus it is prone to misfortunes which then affect the results. So, the device does not achieve the purpose of optimization.
Therefore, it is necessary to provide a device and method for analysis and reading which have simple detection optical path, less interference, simple structure of detection circuit, and accurate readings.